A process for carburizing a steel workpiece to a predetermined surface carbon setpoint value or desired concentration in a fluidized bed oven is known in which in a first carburization step a carburizing gas is used with a C-level above the soot limit and an actual surface carbon content is produced which is above the predetermined surface carbon setpoint or desired value. After that in the fluidized bed oven a diffusion treatment of the workpiece is performed and the actual surface carbon content or value is reduced. Then the carburization step and the diffusion treatment can be repeated if desired.
In the known process (German Pat. No. 35 07 527) the diffusion treatment uses an inert gas. That allows a very exact adjustment of the surface carbon content to a predetermined surface carbon setpoint value or desired content.
If simultaneously the carburized depth or penetration is to be established with precision, difficulties can arise in regard to the simultaneous adjustment of both parameters, because the parameters are physically coupled. Particularly a deeper carburizing depth or penetration demands a comparatively long treatment time.